Vehicle Charger System with Safety Guardian

ABSTRACT

A safety guardian is operable to facilitate notifying an Electronic Vehicle Supply Equipment (EVSE) system whether a vehicle charging system is ready to accept energy. The safety guardian may be configured to facilitate control of a vehicle interface used to provide a reference voltage to the EVSE reflective of whether the charging system is ready to accept energy. The guardian may control the vehicle interface in the absence of a suitable control signal from the vehicle charging system in order to ensure the EVSE is notified when the vehicle charging system is not ready to accept energy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/204,939, filed Aug. 8, 2011, now U.S. Pat. No. ______; the disclosureof which is hereby incorporated in its entirety by reference herein.

TECHNICAL FIELD

The present invention relates to vehicle charging systems, andparticularly to a vehicle charging system of the type that is requiredto provide a reference voltage feedback to an Electric Vehicle SupplyEquipment (EVSE) system to indicate whether the vehicle charging systemis ready to accept energy.

BACKGROUND

An Electric Vehicle Supply Equipment (EVSE) system may be configured tofacilitate charging a high voltage (HV) battery or other energy storageelement used by electric vehicles (EVs), hybrid electric vehicles(HEVs), and plug-in hybrid electric vehicles (PHEVs) to support variousvehicle operations. The EVSE may require a reference voltage or otherindication that a charging system of the vehicle is ready to acceptenergy from the EVSE. In order to prevent false indications of thereadiness of the vehicle charging system to accept energy from the EVSE,a need exists to ensure the EVSE is notified when the vehicle chargingsystem is not ready to accept energy, including during situations inwhich a controller or other element of the vehicle charging system maybe operating improperly.

SUMMARY

One non-limiting aspect of the present invention contemplates a safetyguardian operable with a vehicle interface having a switch operablebetween an open position and a closed position to control a voltage of areference voltage output to an Electronic Vehicle Supply Equipment(EVSE) system, the EVSE system requiring the voltage of the referencevoltage to be greater than a threshold before delivering energy to avehicle charger power plant, the safety guardian being operable to:control the switch to the closed position upon receipt of a first signalfrom a controller associated with the vehicle charger power plant;control the switch to the open position upon receipt of a second signalfrom the controller; and control the switch to the open position in theabsence of the first signal and the second signal.

One non-limiting aspect of the present invention contemplates the safetyguardian being operable to receive the first signal as a pulse widthmodulated (PWM) signal and to output a non-PWM signal to the switch tocontrol the switch between the open and closed positions.

One non-limiting aspect of the present invention contemplates the safetyguardian being operable to control the switch to the open position wheneither one of the first signal and the second signal failed to includean edge within a predefined period of time.

One non-limiting aspect of the present invention contemplates the safetyguardian being operable to control the switch to the open position inthe event power is lost to the controller.

One non-limiting aspect of the present invention contemplates a safetyguardian operable with a vehicle charger system, the vehicle chargersystem including a charger power plant operable to invert AC energyreceived from a mains output of an Electronic Vehicle Supply Equipment(EVSE) system to DC energy sufficient for charging a high voltage (HV)vehicle battery, the EVSE system delivering the AC energy when a firstreference voltage is received and preventing delivery of the AC energywhen a second reference voltage is received, the vehicle charger systemincluding a vehicle interface operable using a control pilot output ofthe EVSE to generate the first reference voltage when the charger powerplant is ready to charge the vehicle battery and to output the secondreference voltage when the charger power plant is not ready to chargethe vehicle battery, the vehicle interface including a first switchoperable between an open position and a closed position and a secondswitch operable between an open position and a closed position, thevehicle interface generating the first reference voltage when the firstand second switches are both in the closed position and the secondreference voltage when either one of the first and second switches arein the open position, the vehicle charger system including a controlleroperable to output a first signal to control the first switch betweenthe open and closed positions and a second signal to control the secondswitch between the open and closed positions according to whether thecharger power plant is ready to charge the vehicle battery, the safetyguardian including: a device operable to intercept the first signaloutput from the safety controller and to output a third signal to thefirst switch, the third signal being based on the first signal andoperable to control the first switch between the open position and theclosed position according to whether the charger power plant is ready tocharge the vehicle battery, the device being operable in the absence ofthe first signal to automatically generate the third signal such thatthe first switch is controlled to the open position.

One non-limiting aspect of the present invention contemplates the deviceis a retriggerable monostable.

One non-limiting aspect of the present invention contemplates theretriggerable monostable generates the third signal to control the firstswitch to the open position when the first signal fails to include anedge within a pre-defined period of time.

One non-limiting aspect of the present invention contemplates theretriggerable monostable generates the third signal to control the firstswitch to the closed position when the first signal includes an edgewithin a pre-defined period of time.

One non-limiting aspect of the present invention contemplates the firstsignal alternates between a first voltage and a second voltage at afirst frequency and the third signal alternates between a third voltageand a fourth voltage depending on the first frequency, the third signalhaving the third voltage when the first frequency is greater than athreshold and the third signal having the fourth voltage when the firstfrequency is less than the threshold.

One non-limiting aspect of the present invention contemplates a voltageregulator configured to maintain operation of the device when thecontroller loses power while energy is still available from a lowvoltage (LV) vehicle battery.

One non-limiting aspect of the present invention contemplates chargersystem including: a charger power plant operable to invert AC energyreceived from a mains output of an EVSE system to DC energy sufficientfor charging a high voltage (HV) vehicle battery; an input operable toreceive a control pilot from the EVSE system; a vehicle interfaceoperable with the input to generate a first reference signal using thecontrol pilot when the charger power plant is ready to invert the ACenergy to the DC energy and to generate a second reference signal usingthe control pilot when the charger power plant is not ready to invertthe AC energy to the DC energy, the vehicle interface including a firstswitch operable between an open position and a closed position and asecond switch operable between an open position and a closed position,wherein the vehicle interface generates the first reference signal whenthe first and second switches are both in the closed position and thesecond reference signal when either one of the first and second switchesare in the open position; a safety controller operable to output a firstsignal for controlling the first switch between the open position andthe closed position; a vehicle charger controller operable to output asecond signal to the second switch, the second signal controlling thesecond switch between the open position and the closed position; and asafety guardian operable to receive the first signal output from thesafety controller, the safety guardian operable to output a third signalto the first switch, the third signal being based on the first signaland operable to control the first switch between the open position andthe closed position.

One non-limiting aspect of the present invention contemplates the safetyguardian includes a retriggerable monostable operable to generate thethird signal based on the first signal.

One non-limiting aspect of the present invention contemplates theretriggerable monostable generates the third signal to control the firstswitch to the open position when the first signal fails to include anedge within a pre-defined period of time.

One non-limiting aspect of the present invention contemplates theretriggerable monostable generates the third signal to control the firstswitch to the closed position when the first signal includes an edgewithin a pre-defined period of time.

One non-limiting aspect of the present invention contemplates the firstsignal alternates between a first voltage and a second voltage at afirst frequency and the third signal alternates between a third voltageand a fourth voltage depending on the first frequency, the third signalhaving the third voltage when the first frequency is greater than athreshold and the third signal having the fourth voltage when the firstfrequency is less than the threshold.

One non-limiting aspect of the present invention contemplates the firstvoltage equals the third voltage.

One non-limiting aspect of the present invention contemplates a firstpower supply unit (PSU) operable to power the safety controller and aseparate, second PSU operable to power the vehicle charger controller,each of the first PSU and second PSU regulate current from a low voltage(LV) vehicle battery to facilitate powering the respective one of thesafety controller and the charger controller.

One non-limiting aspect of the present invention contemplates the safetyguardian regulates current from the LV vehicle battery to facilitategenerating the third signal, the safety guardian regulating current fromthe LV battery separately and independently from the first PSU and thesecond PSU.

One non-limiting aspect of the present invention contemplates thevehicle interface includes a first resistor and a second resistorarranged relative to the first switch and the second switch such thatthe first resistor and a second resistor are connected in parallel onlywhen both of the first switch and the second switch are in the closedposition.

One non-limiting aspect of the present invention contemplates the firstand second switches are connected in series with the second resistor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is pointed out with particularity in the appendedclaims. However, other features of the present invention will becomemore apparent and the present invention will be best understood byreferring to the following detailed description in conjunction with theaccompany drawings in which:

FIG. 1 illustrates a charging system having an Electric Vehicle SupplyEquipment (EVSE) system configured to provide energy to a vehiclecharging system.

FIG. 2 illustrates a charging system with a safety guardian inaccordance with one non-limiting aspect of the present invention.

FIG. 3 illustrates the safety guardian as configured as a retriggerablemonostable in accordance with one non-limiting aspect of the presentinvention.

FIG. 4 illustrates a first signal input to the retriggerable monostableand a third signal output from the retriggerable monostable inaccordance with one non-limiting aspect of the present invention.

FIG. 5 illustrates a charging system where a safety controller has beeneliminated in accordance with one non-limiting aspect of the presentinvention.

FIG. 6 illustrates a charging system where a first switch has beeneliminated in accordance with one non-limiting aspect of the presentinvention.

DETAILED DESCRIPTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely exemplary of the invention that may be embodied in various andalternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

FIG. 1 illustrates a charging system 10 having an Electric VehicleSupply Equipment (EVSE) system 12 configured to provide energy to avehicle charging system 14. EVSE system 12 may be configured to provideAC energy to a charger power plant 16 on the vehicle for conversion toDC energy sufficient for charging a high voltage (HV) battery or otherelectronic storage element. EVSE system 12 may be associated with a walloutlet system or other system sufficiently configured to provide ACenergy to charger power plant 16, such as in the manner described withinSAE J1772, the disclosure of which is hereby incorporated by referencein its entirety. In addition to or in place of detection logic or otherfeatures, EVSE system 12 may include a control pilot circuit 18 throughwhich vehicle charging system 14 is required to communicate whethercharger power plant 16 is ready to receive the AC energy.

A cordset (not shown) may be configured to facilitate connecting EVSEsystem 12 to a receptacle (not shown) included within the vehicle. Thereceptacle may include an input for connecting to a mains input, acontrol pilot input 22 for connecting to the control pilot circuit, anda ground input 24 for connecting the vehicle ground to utilities/earthground. Control pilot circuit 18 may be a low voltage and/or low currentsystem and electrically isolated from the mains input 20. Onceconnected, control pilot circuit 18 may be used to generate a voltagereference and a voltage measurement node 30 to reflect whether chargerpower plant 16 is ready to receive DC energy through the mainsconnection. A controller (not shown) associated with EVSE system 12 maypermit or deny delivery of the AC energy to the mains connectiondepending on the reference voltage.

Control pilot circuit 18 may include an oscillator 32 configured tooutput a control pilot signal. A vehicle interface portion 34 of thecontrol pilot circuit included on the vehicle may receive the controlpilot signal from oscillator 32. Vehicle interface 34 may include afirst resistor 36 and a second resistor 38 connectable in series with afirst switch 40 and a second switch 42. First switch 40 and secondswitch 42 may be operable between an open position and a closed positiondepending on whether a corresponding first and second signal 39, 41 isdelivered at a high state (first voltage, e.g., 5V) or a low state(second voltage, e.g., 0V). The closed position may correspond toswitches 40, 42 conducting current and the open position may correspondwith switches 40, 42 being unable to conduct current. Of course, the“on” and “off” switch voltages may be set with application voltages thatdepend on the physical implementation of the vehicle interface (e.g.,bipolars, MOSFETs, relays, etc.). In the absence of a contrary command,first and second switches 40, 42 may be configured to maintain theircurrent position, i.e., to remain in one of the open and closedpositions when no signal is received commanding the switch to changepositions.

The voltage measured at voltage measurement node 30 may vary dependingon whether first resistor 36 and second resistor 38 are connected inparallel. An EVSE controller (not shown) may be configured to adjustand/or prevent delivery of the AC energy to the mains connectiondepending on whether the voltage at voltage measurement node 30 is at afirst reference voltage or a second reference voltage. The firstreference voltage may be associated with first and second switches 40,42 being in the closed position such that first and second resistors 36,38 are connected in parallel. The second reference voltage may beassociated with either one of first and second switches 40, 42 being inthe open position such that the second resistor 38 is disconnected fromthe rest of the control pilot circuit. Vehicle charging system 14 mayinclude a safety controller 44 and a vehicle charger controller 46 tofacilitate respectively outputting first and second signals 39, 41 tothe corresponding first and second switches 40, 42.

Vehicle charger controller 46 may be a Micro-Controller Unit (MCU)configured to monitor various operating conditions of charger powerplant 16 in order to assess whether charger power plant 16 is ready toreceive AC energy from EVSE system 12. Vehicle charger controller 46 mayalso be configured to control various charging operations of chargerpower plant 16, including assessing whether the HV battery or otherelement being charged is sufficiently charged or other conditions inwhich further delivery of the AC energy from EVSE system 12 isundesirable. Upon completion of the charging event or other condition,vehicle charger controller 46 may adjust second signal 41 in a mannersufficient to open second switch 42, and thereby change the referencevoltage and notify the EVSE controller to cease further delivery of ACenergy. Optionally, vehicle charging system 14 may include other meansfor communicating completion of the charging event to EVSE system 12such that the operations associated with opening second switch 42 may beredundant or secondary means for ensuring the EVSE controller isinstructed to cease delivery of AC energy.

Vehicle charger controller 46 may also communicate a signal 50 to safetycontroller 44 indicating whether first switch 40 should be controlled tothe open or closed position. The signal may be the same as second signal41 communicated to second switch 42 and/or it may be a different signal,such as a data message or data packets having information usable bysafety controller 44 to assess whether vehicle charger controller 46 orthe vehicle charging system is operating improperly. Safety controller44 may be a Field Programmable Gate Array (FPGA) program with theability to override commands of vehicle charger controller 46 or tootherwise assess improper operations in order to ensure that firstswitch 40 can be opened independently of second switch 42 beingcommanded to closed position, such as to prevent delivery of the ACenergy when the vehicle charging system is operating improperly.

Optionally, safety controller 44 may be configured to provide statusinformation or other information to vehicle charger controller 46 thatvehicle charger controller 46 can use to assess whether the safetycontroller is operating properly. This information can be useful inallowing vehicle charger controller 46 to open second switch 42 whensafety controller 44 is unable to properly control first switch 40, suchas when power is lost to safety controller 44. Safety controller 44 andvehicle charger controller 46 are shown to be separately connected toindependent power supply units (PSUs) 54, 56 in order to ameliorate thepossibility of both controllers 44, 46 simultaneously losing power whileboth of first and second switches 40, 42 are in the closed position.First and second PSUs 54, 56 are shown to have separate connections 58,60 to a low-voltage (LV) battery (not shown) such that each PSU 54, 56is responsible for processing current from the LV battery for use inpowering its controller.

FIG. 2 illustrates a charging system 60 with a safety guardian 62 inaccordance with one non-limiting aspect of the present invention. Safetyguardian 62 may be included to ensure at least one of first and secondswitches 40, 42 is able to be controlled to the open position withouthaving to include multiple PSUs. A single PSU 64 is believed to bebeneficial over the dual PSU configuration since it improves cost, powerdensity (i.e., space needed), and reliability (i.e., each extracomponent can contribute to more faults (ppms) to the whole systemreliability). Advantageously, safety guardian 62 operates in cooperationwith safety controller 44 and vehicle charger controller 46 such thatsafety guardian 62 may be added to the system shown in FIG. 1 withouthaving to make significant modifications. Safety guardian 62 may beconfigured to intercept first signal 39 output from safety controller 44and to output a corresponding third signal 68 to first switch 40, i.e.,to control first switch 40 to the desired open or closed position.

Safety controller 44 in the system of FIG. 2 may be configured to outputfirst signal 39 as a pulse-width modulated (PWM) signal instead of thenon-PWM signal shown in the system of FIG. 1. PWM signal 39 may includea plurality of edges such that the PWM signal acts as a “heartbeat”.Safety guardian 62 may convert the received PWM signal 39 to non-PWMsignal 68 used to control first switch 40 between the open and closedposition. Safety guardian 62 may be configured to control first switch40 to the open position, i.e., to generate third signal 68 at a highstate, as long as a sufficient number of edges are detected to be withinfirst signal 39. In the event first signal 39 fails to include asufficient number of edges, safety guardian 62 may be configured toautomatically open first switch 40, i.e., to generate third signal 68 ata low state when the desired “heartbeat” is not detected. Safetycontroller 62 may be configured in a manner similar to that describedabove with respect to assessing whether it is desirable to control firstswitch 40 to the open or closed position.

The edge-detection employed by safety guardian 62 may limit complexityin that safety guardian 62 may not need to assess vehicle chargingsystem operations or otherwise processed data from safety controller 44and/or vehicle charger controller 46. It may simply assess whether asufficient PWM signal is being received, and if not, to automaticallyopen first switch 40. The edge-detection employed by safety guardian 62is also believed to be preferred over fixed-level detection systemssince such systems can output a fixed level value when operatingimproperly, whereas the PWM/isolating method safety guardian is lesslikely to result in a fixed level output causing a switch to remainopen. Safety controller 44 and/or vehicle charger controller 46 mayinclude the same or similar capabilities described above with respect toassessing various vehicle charging system characteristics and operatingstates when determining whether to continue or discontinue AC energydelivery to the charger power plant, i.e., whether the charger powerplant is ready to receive AC energy. Safety controller 44 may beslightly modified to output the PWM signal instead of the non-PWM signalpreviously communicated directly to the first switch to directly controlits movement between the open and closes positions.

FIG. 3 illustrates the safety guardian 62 as having a retriggerablemonostable 72 in accordance with one non-limiting aspect of the presentinvention. Retriggerable monostable 72 may be configured to output thirdsignal 68 to first switch 40 depending on first signal 39 received fromsafety controller 44. FIG. 4 illustrates first signal 39 input toretriggerable monostable 72 and third signal 68 output fromretriggerable monostable 72. As shown, retriggerable monostable 72outputs third signal 68 at a high state whenever a sufficient number ofedges are received within a predefined period of time in order tocontrol first switch 40 to the closed position. Once the number of edgesceases or fails to occur within a sufficient period of time, retriggablemonostable 72 outputs third signal 68 at a low state such that firstswitch 40 is controlled to the open position.

Retriggerable monostable 72 may be configured to generate a pulse ofwidth Trm every time that a rising edge is detected at its input (alsocan be configured to work with falling edges). If another rising edgeappears prior to the end of the output pulse, then this output pulse maybe extended another Trm miliseconds from the last positive input edge.By providing a sequence of edges at the input, the output can be kept inan active value permanently. If the input signal stops (i.e. remains ina fixed value) then the output of the circuit becomes inactive after Trmmiliseconds from the last positive edge, i.e., it transitions to the lowstate. This behavior may be useful to automatically managing firstswitch 40 to the open position when a disruption occurs within vehiclecharger system 14 that results in safety controller 44 eitherintentionally or unintentionally failing to provide a sufficient PWMsignal to maintain first switch 40 is open position.

Retriggerable monostable 72 is shown to include an independent andseparate connection 74 to the LV battery. A voltage regulator 76 may beincluded to facilitate processing of current received from the LVbattery. A resistor 78 and a capacitor 80 are also shown to indicatehardware components used to adjust operation of retriggerable monostable72. By adjusting the values of resistor 78 and capacitor 80,retriggerable monostable 72 adjusts the number of edges that must bedetected in order to maintain third signal 68 in the high state, i.e.,the length of Trm. This type of configuration, i.e. a hardware-basedconfiguration, may be beneficial over software or other programmableconfiguration in that it may be less susceptible to operatingdisruptions, particularly those associated with software-basedapplications and controls. While the present invention describes safetyguardian 62 as a retriggerable monostable 72, this is done for exemplaryand non-limiting purposes, as the present invention fully contemplatessafety guardian 62 including any sufficiently configured device tosupport the operations contemplated herein.

FIG. 5 illustrates a charging system 90 where the safety controller hasbeen eliminated in accordance with one non-limiting aspect of thepresent invention. The elimination of the safety controller may bebeneficial in reducing system cost and complexity. Vehicle chargercontroller 46 may be configured to implement some or all of theoperations previously implemented with the safety controller, e.g.,monitoring various safety-related operating characteristics for use inassessing whether the first switch should be controlled to the openposition. Safety guardian 62 may operate in the same manner describedabove with respect to FIG. 4.

FIG. 6 illustrates a charging system 94 where the first switch has beeneliminated in accordance with one non-limiting aspect of the presentinvention. The elimination of the first switch may be beneficial insimplifying the configuration of pilot control circuit 18. System 94 mayoperate similarly to the systems described above with respect to safetyguardian 62 requiring a sufficient PWM signal in order to output anon-PWM signal sufficient to control second switch 42 to the closedposition such that second switch 42 is automatically controlled to theopen position in the absence of the sufficient PWM signal.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A charger system comprising: a charger powerplant operable to invert AC energy received from a mains output of anElectronic Vehicle Supply Equipment (EVSE) system to DC energysufficient for charging a high voltage (HV) vehicle battery; an inputoperable to receive a control pilot from the EVSE system; a vehicleinterface operable with the input to generate a first reference signalusing the control pilot when the charger power plant is ready to invertthe AC energy to the DC energy and to generate a second reference signalusing the control pilot when the charger power plant is not ready toinvert the AC energy to the DC energy, the vehicle interface including afirst switch operable between an open position and a closed position anda second switch operable between an open position and a closed position,wherein the vehicle interface generates the first reference signal whenthe first and second switches are both in the closed position and thesecond reference signal when either one of the first and second switchesare in the open position; a safety controller operable to output a firstsignal for controlling the first switch between the open position andthe closed position; a vehicle charger controller operable to output asecond signal to the second switch, the second signal controlling thesecond switch between the open position and the closed position; and asafety guardian operable to receive the first signal output from thesafety controller, the safety guardian operable to output a third signalto the first switch, the third signal being based on the first signaland operable to control the first switch between the open position andthe closed position.
 2. The system of claim 1 wherein the safetyguardian includes a retriggerable monostable operable to generate thethird signal based on the first signal.
 3. The system of claim 2 whereinthe retriggerable monostable generates the third signal to control thefirst switch to the open position when the first signal fails to includean edge within a pre-defined period of time.
 4. The system of claim 2wherein the retriggerable monostable generates the third signal tocontrol the first switch to the closed position when the first signalincludes an edge within a pre-defined period of time.
 5. The system ofclaim 2 wherein the first signal alternates between a first voltage anda second voltage at a first frequency and the third signal alternatesbetween a third voltage and a fourth voltage depending on the firstfrequency, the third signal having the third voltage when the firstfrequency is greater than a threshold and the third signal having thefourth voltage when the first frequency is less than the threshold. 6.The system of claim 5 wherein the first voltage equals the thirdvoltage.
 7. The system of claim 1 further comprising a first powersupply unit (PSU) operable to power the safety controller and aseparate, second PSU operable to power the vehicle charger controller,each of the first PSU and second PSU regulate current from a low voltage(LV) vehicle battery to facilitate powering the respective one of thesafety controller and the charger controller.
 8. The system of claim 7wherein the safety guardian regulates current from the LV vehiclebattery to facilitate generating the third signal, the safety guardianregulating current from the LV battery separately and independently fromthe first PSU and the second PSU.
 9. The system of claim 1 wherein thevehicle interface includes a first resistor and a second resistorarranged relative to the first switch and the second switch such thatthe first resistor and the second resistor are connected in parallelonly when both of the first and second switches are in the closedposition.
 10. The system of claim 9 wherein the first switch and thesecond switch are connected in series with the second resistor.